从‘void*(*)()’到‘void*(*)(void*)’的转换无效[-fpermissive]

Question

我已经在这个程序上工作了一整天，但是我不能纠正我的错误。我已经在互联网上到处寻找了一个充分的答案，但我不确定我做错了什么。我已经尝试了我能想到的所有方法来消除我的代码中的这些错误。我只需要让程序运行！

我为我糟糕的代码道歉。C/C++确实不是我的强项。

以下是我尝试运行时收到的错误列表：

hotel.c: In function ‘int main(int, char**)’:
hotel.c:228:53: error: invalid conversion from ‘void* (*)()’ to ‘void* (*)(void*)’ [-fpermissive]
     pthread_create(&receptionIn, NULL, Checkin, NULL);

In file included from hotel.c:1:0:
/usr/include/pthread.h:244:12: error:   initializing argument 3 of ‘int pthread_create(pthread_t*, const pthread_attr_t*, void* (*)(void*), void*)’ [-fpermissive]
 extern int pthread_create (pthread_t *__restrict __newthread,

hotel.c:229:55: error: invalid conversion from ‘void* (*)()’ to ‘void* (*)(void*)’ [-fpermissive]
     pthread_create(&receptionOut, NULL, Checkout, NULL);

In file included from hotel.c:1:0:
/usr/include/pthread.h:244:12: error:   initializing argument 3 of ‘int pthread_create(pthread_t*, const pthread_attr_t*, void* (*)(void*), void*)’ [-fpermissive]
 extern int pthread_create (pthread_t *__restrict __newthread,

hotel.c:233:19: error: request for member ‘guest_id’ in ‘guests[t]’, which is of non-class type ‘pthread_t {aka long unsigned int}’
         guests[t].guest_id = t;

hotel.c:234:19: error: request for member ‘room’ in ‘guests[t]’, which is of non-class type ‘pthread_t {aka long unsigned int}’
         guests[t].room = 0;

hotel.c:235:19: error: request for member ‘guestCheckIn’ in ‘guests[t]’, which is of non-class type ‘pthread_t {aka long unsigned int}’
         guests[t].guestCheckIn = 0;

hotel.c:236:19: error: request for member ‘guestCheckOut’ in ‘guests[t]’, which is of non-class type ‘pthread_t {aka long unsigned int}’
         guests[t].guestCheckOut = 0;

hotel.c:237:28: error: request for member ‘hasRoom’ in ‘guests[t]’, which is of non-class type ‘pthread_t {aka long unsigned int}’
         sem_init(guests[t].hasRoom, 0, 0);

hotel.c:238:28: error: request for member ‘checkedOut’ in ‘guests[t]’, which is of non-class type ‘pthread_t {aka long unsigned int}’
         sem_init(guests[t].checkedOut, 0, 0);

第233-238行的错误看起来像是相关的错误，但我不知道是什么导致了它们。我尝试将格式更改为...

guestst->guest_id = t；

...but我得到了不同的错误。

我在这里四处寻找可能会有帮助的答案，但我找不到一个能充分解释它的答案。

请帮帮我！

#include <pthread.h>
#include <semaphore.h>
#include <stdio.h>
#include <stdlib.h>

// Structure for tracking the status of a guest.
struct guest
{
    // Variable for tracking which guest/thread this is.
    int guest_id;

    // Variable for tracking which room a guest is assigned.
    int room;

    // Variable for determining if a guest is ready to check in.
    int guestCheckIn;

    // Variable for determining if a guest is ready to check out.
    int guestCheckOut;

    // Semaphore for keeping track of whether the guest has a room.
    sem_t hasRoom;

    // Semaphore for keeping track of whether the guest is still at the hotel.
    sem_t checkedOut;
};

struct guest guests[10];

// Array for tracking which rooms are available.
int rooms[5];

// Variable for keeping track of how many times the pool was used.
int poolUse = 0;

// Variable for keeping track of how many times the restaurant was used.
int restaurantUse = 0;

// Variable for keeping track of how many times the fitness center was used.
int fitnessCenterUse = 0;

// Variable for keeping track of how many times the business center was used.
int businessCenterUse = 0;

// Semaphore for tracking if the check-in receptionist is busy.
sem_t checkInBusy;
// Variable for determining if a guest wants to check in.
sem_t readyForCheckIn;

// Semaphore for tracking if the check-out receptionist is busy.
sem_t checkOutBusy;
// Variable for determining if a guest wants to check out.
sem_t readyForCheckOut;

// Semaphore for tracking how many available rooms there are.
sem_t numRooms;

/**
*  This procedure 
**/
void *Checkin()
{
    while(true)
    {
        // Wait if receptionist is already busy.
        sem_wait(&checkInBusy);

        // Wait for a guest to be ready to check in.
        sem_wait(&readyForCheckIn);

        // Variable for storing index of available guest.
        int readyGuest = 11;

        // Find a guest that is ready for check in.
        for(int x = 0; x < 10; x++)
        {
            if(guests[x].guestCheckIn == 1 && readyGuest > x)
            {
                readyGuest = x;
            }
        }

        printf("The check-in reservationist greets Guest %d\n", readyGuest);

        // Variable for storing the available room.
        int available = 0;

        // Find the guest an available room.
        for(int y = 0; y < 5; y++)
        {
            if(rooms[y] == 0 && available != 0)
            {
                available = y;
            }
        }

        // Grant the room  to the guest.
        printf("Assign room %d to Guest %d\n", available, readyGuest);
        guests[readyGuest].room = available;
        rooms[available] = readyGuest;
        sem_post(&guests[readyGuest].hasRoom);

        // Guest is now checked in and no longer needs to be ready to do so.
        guests[readyGuest].guestCheckIn = 0;

        // Increment the corresponding semaphore to indicate that check-in is no longer busy.
        sem_post(&checkInBusy);
    }
}

/**
*  
**/
void *Checkout()
{
    while(true)
    {
        // Wait if receptionist is already busy.
        sem_wait(&checkOutBusy);

        // Wait for a guest to be ready to check out.
        sem_wait(&readyForCheckOut);

        // Variable for storing index of available guest.
        int readyGuest = 11;

        // Find a guest that is ready for check out.
        for(int x = 0; x < 10; x++)
        {
            if(guests[x].guestCheckOut == 1 && readyGuest > x)
            {
                readyGuest = x;
            }
        }

        // Free up the room the guest occupied.
        rooms[guests[readyGuest].room] = 0;
        printf("The check-out greets Guest %d and receives the key from room %d\n", readyGuest, guests[readyGuest].room);
        printf("Calculate the balance for Guest %d\n", readyGuest);
        printf("Receive $1 from Guest %d and complete the check-out\n", readyGuest);

        // Guest is now checked out and no longer needs to be ready to do so.
        guests[readyGuest].guestCheckOut = 0;

        // Increment the corresponding semaphore to indicate that check-out is no longer busy.
        sem_post(&checkOutBusy);
    }
}

/**
*  A guest will attempt to reserve a room but will wait until there is an available room before approaching the receptionist. 
*  If a room is available, they will approach the check-in, get a room and then proceed to do their hotel thing. Once 
*  finished, the guest will go to the check out and return the room key.
**/
void *Guest(void *threadarg)
{
    struct guest *guest_data;

    // Wait if there are no available rooms.
    sem_wait(&numRooms);

    // Declare guest is ready to be checked in and increment the corresponding semaphore.
    printf("Guest %d waits for check-in...", guest_data->guest_id);
    guest_data->guestCheckIn = 1;
    sem_post(&readyForCheckIn);

    // Wait until a room is assigned.
    sem_wait(&guest_data->hasRoom);
    printf("Guest %d receives Room %d and completes check in\n", guest_data->guest_id, guest_data->room);

    // Guest goes to do hotel stuff!
    // Generate a random number between 0-3.
    int r = rand() % 4;

    // Go to pool!
    if(r == 0)
    {
        printf("Go to hotel swimming pool\n");
        poolUse++;
    }

    // Go to restaurant!
    if(r == 1)
    {
        printf("Go to hotel restaurant\n");
        restaurantUse++;
    }

    // Go to fitness center!
    if(r == 2)
    {
        printf("Go to hotel fitness center\n");
        fitnessCenterUse++;
    }

    // Go to business center!
    if(r == 4)
    {
        printf("Go to hotel business center\n");
        businessCenterUse++;
    }

    // Declare a guest is ready to be checked out and increment the corresponding semaphore.
    guest_data->guestCheckOut = 1;
    sem_post(&readyForCheckOut);

    // Wait until a guest is completely checked out.
    sem_wait(&guest_data->checkedOut);
    printf("Guest %d receives the total balance of $1\n", guest_data->guest_id);
    printf("Guest %d makes a payment\n", guest_data->guest_id);
}

/**
*  The main procedure creates the threads for the 
**/
int main(int argc, char *argv[])
{
    pthread_t guests[10];
    pthread_t receptionIn;
    pthread_t receptionOut;

    sem_init(&checkInBusy, 0, 1);
    sem_init(&readyForCheckIn, 0, 0);
    sem_init(&checkOutBusy, 0, 1);
    sem_init(&readyForCheckOut, 0, 0);
    sem_init(&numRooms, 0, 5);

    pthread_create(&receptionIn, NULL, Checkin, NULL);
    pthread_create(&receptionOut, NULL, Checkout, NULL);    

    for(int t = 0; t < 10; t++)
    {
        guests[t].guest_id = t;
        guests[t].room = 0;
        guests[t].guestCheckIn = 0;
        guests[t].guestCheckOut = 0;
        sem_init(guests[t].hasRoom, 0, 0);
        sem_init(guests[t].checkedOut, 0, 0);

        pthread_create(&guests[t], NULL, Guest, (void *) &guests[t]);
    }
}

Answer 1

• 函数Checkin和Checkout的签名不适合用作pthread的线程函数。使用正确的类型。也就是说，让函数有一个void*参数，
• ，main()中的局部变量pthread_t guests[10];隐藏了全局变量struct guest guests[10];。重命名局部变量以避免冲突。

Answer 2

您的receptionIn()和receptionOut()函数不带任何参数：

 void *Checkin()

 void *Checkout()

它们被传递给pthread_create()。

 pthread_create(&receptionIn, NULL, Checkin, NULL);
 pthread_create(&receptionOut, NULL, Checkout, NULL);

您需要做的是查看pthread_create()函数的文档，以及它需要哪种类型的函数指针。它不接受指向没有任何参数的函数的指针。